The present disclosure relates to aircraft environmental control systems. More specifically, the present disclosure relates to a vane for a variable diffuser in a cabin air compressor.
Air cycle machines are used in environmental control systems in aircraft to condition air for delivery to an aircraft cabin. Conditioned air is air at a temperature, pressure, and humidity desirable for aircraft passenger comfort and safety. At or near ground level, the ambient air temperature and/or humidity is often sufficiently high that the air must be cooled as part of the conditioning process before being delivered to the aircraft cabin. At flight altitude, ambient air is often far cooler than desired, but at such a low pressure that it must be compressed to an acceptable pressure as part of the conditioning process. Compressing ambient air at flight altitude heats the resulting pressured air sufficiently that it must be cooled, even if the ambient air temperature is very low. Thus, under most conditions, heat must be removed from air by the air cycle machine before the air is delivered to the aircraft cabin.
A cabin air compressor can be used to compress air for use in an environmental control system. The cabin air compressor includes a motor to drive a compressor section that in turn compresses air flowing through the cabin air compressor. A variable diffuser is also positioned in the cabin air compressor. The variable diffuser has a plurality of vanes that are configured to pivot about a point in order to vary the size of a gap between adjacent vanes to vary the flow of air through the variable diffuser. The plurality of vanes on the variable diffuser are held between a shroud and a backing plate. A small clearance is typically provided between the shroud and the vanes and between the shroud and the backing plate, which can cause the vanes to float freely. Under unstable airflow conditions, the vanes may dither, vibrate, or resonate if they are floating freely. This can lead to significant wear between the vanes and the shroud and between the vanes and the backing plate and can also cause failure of the vanes.